EP1745908B1 - Method for producing fibre reinforced hollow objects with a water dispersible core - Google Patents

Method for producing fibre reinforced hollow objects with a water dispersible core Download PDF

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Publication number
EP1745908B1
EP1745908B1 EP20060009821 EP06009821A EP1745908B1 EP 1745908 B1 EP1745908 B1 EP 1745908B1 EP 20060009821 EP20060009821 EP 20060009821 EP 06009821 A EP06009821 A EP 06009821A EP 1745908 B1 EP1745908 B1 EP 1745908B1
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EP
European Patent Office
Prior art keywords
support core
weight
binding agent
filler
starch
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
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EP20060009821
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German (de)
French (fr)
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EP1745908A1 (en
Inventor
Bruno Niesner
Stefan Kerscher
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Bayerische Motoren Werke AG
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Bayerische Motoren Werke AG
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Publication of EP1745908A1 publication Critical patent/EP1745908A1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
    • B29C33/52—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles soluble or fusible
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/40—Shaping or impregnating by compression not applied
    • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/44—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding
    • B29C70/443—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding and impregnating by vacuum or injection
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/40—Shaping or impregnating by compression not applied
    • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/46—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
    • B29C70/48—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs and impregnating the reinforcements in the closed mould, e.g. resin transfer moulding [RTM], e.g. by vacuum

Definitions

  • the invention relates to a method for producing a structural hollow component made of fiber-reinforced plastic according to the preamble of claim 1.
  • RTM Resin Transfer Molding
  • At least one layer of e.g. uni- or bidirectionally directed reinforcing fibers placed between the upper and lower tool of a heated press and impregnated the fiber layer with a thermosetting plastic, such as an epoxy resin with hardener, which is injected under pressure into the cavity with the fiber layer between the upper and lower tool.
  • a thermosetting plastic such as an epoxy resin with hardener
  • the vacuum-injection method is used, in which instead of pressure, a vacuum is applied to suck the thermosetting plastic in the fiber layer.
  • supporting cores have been used from low-melting bismuth alloys. Because of the high energy consumption for melting the cores, the high weight and the resulting difficult handling, but also because of the health risk of bismuth vapors, these cores are not used in practice.
  • support cores made of high-density foam are used, which remain in the component and thus lead to a corresponding increase in weight.
  • WO 02/072328 A1 is already a support core according to the preamble of claim 1 is known.
  • polyvinylpyrrolidone is used as the water-soluble organic binder and in particular ceramic hollow spheres with a diameter of about 120 ⁇ m as the filler.
  • the suspension of water, binder and filler is filled in a porous mold as in slip casting to allow the water to drain.
  • the support core is then demolded and dried at 120 ° C for several hours.
  • a braiding system can be used, wherein the support core is in the eye of the braiding system, while the reinforcing threads are removed under high voltage from the periphery.
  • the support core keeps up WO 02/072328 A1 higher thread withdrawal forces but not stood.
  • a water-dispersible support core is made of a water-soluble organic binder and a filler.
  • the filler consists of more than 50% by weight of sand.
  • the organic binder is a carbohydrate, for example starch.
  • US-A-5492660 a method according to the preamble of claim 1 is described.
  • hollow carbon spheres are used as the filler for the support core, and inorganic binders, such as sodium silicate, as well as binders based on alumina, so that the support core can be dispersed only with strong acids, such as hydrochloric acid.
  • the object of the invention is a method provide, with the complex fiber-reinforced structural hollow components of high strength and dimensional stability can be produced in a short time.
  • a support core of high strength is used.
  • the 3-point strength of the support core is preferably more than 500 N / cm 2 , in particular more than 600 N / cm 2 .
  • a braiding system can be used, in whose eye the support core is, while the'Verstärkungsfäden be removed under high voltage from the periphery. Thanks to him high strength, the support core easily withstands these high pull-off forces.
  • the support core according to the invention a high dimensional stability of the structural hollow components produced therewith is achieved, in particular by the RTM method, and this also applies to complex components. This is due to the high compressive strength of the support core according to the invention.
  • the injection pressure to which the support core wrapped with the fiber layer is normally 50 bar or less, whereas for complex components having a correspondingly higher fiber volume content, an injection pressure of 80 bar and more is required, so that the thermosetting plastic on the fiber layer properly impregnated the support core.
  • the support core is characterized by a compressive strength of 80 bar, in particular 100 bar and more. He is therefore able to withstand high injection pressures in the RTM process easily.
  • the proportion of the binder is preferably less than 10 wt .-%, in particular less than 5 wt .-%, based on the weight of the filler. This has a corresponding reduction of the water content and thus a short drying time with a correspondingly short production time of the support core and thus short cycle times result. In cases where drying time is not critical, For example, in the prototype production, but also higher binder contents can be used.
  • the proportion of the binder of the support core is preferably at least 2 wt .-%, based on the weight of the filler in order to achieve a sufficient strength.
  • sand preferably quartz sand is used, but other SMFe are used for the production of the support core, such as zircon sand or Cerabead.
  • the mean grain size of the sand is preferably between 100 .mu.m and 800 .mu.m, in particular between 200 .mu.m and 500 .mu.m.
  • the support core can be used with a core shooter, as for example in DE 102 00 927 A1 is injected into the mold with compressed air, because the sand ensures the required flowability or fluidizability of the molding material.
  • the support core can be made by pressing, for example with a mold, wherein the molding material is pressed with a piston in the mold.
  • the filler can be made entirely of sand, but as a filler and a mixture can be used, which consists of sand and expanded glass granules.
  • Expanded glass granulate is a glass recycling product that is used in particular for sound and heat insulation. To produce expanded glass granules, scrap glass is ground, the glass powder formed in the process is mixed with water, binding agent and blowing agent, and the spherical granules are formed from this by foaming the blowing agent in a rotary kiln at about 900 ° C.
  • the mean grain size of the expanded glass granules is preferably 100 .mu.m to 800 .mu.m, in particular 200 .mu.m to 500 .mu.m.
  • the sand can also be mixed with other fillers, for example with hollow spheres, such as hollow ceramic spheres, e.g. with a mean diameter of 50 m to 400 ⁇ m.
  • hollow spheres such as hollow ceramic spheres, e.g. with a mean diameter of 50 m to 400 ⁇ m.
  • mixtures of sand, expanded glass granules and hollow spheres can be used as filler for the support core.
  • the proportion of the sand of the support core is more than 50 wt .-% of the filler, preferably more than 70 wt .-%, in particular 90 wt .-% and more.
  • a polysaccharide binder As the organic binder, a polysaccharide binder is used.
  • the polysaccharide binder may be a cellulose based binder, especially carboxymethylcellulose.
  • a starch-based binder is used as polysaccharide binder, in particular starch ether, since a starch-based binder at the same weight fraction leads to a particularly high strength.
  • blends of a cellulose-based binder and a starch-based binder e.g. from carboxymethyl cellulose and starch ether, can be used.
  • the proportion of the starch-based binder is preferably more than 70% by weight of the binder.
  • a binder which consists entirely, that is more than 97% by weight, of a starch-based binder, ie in particular starch ether, is generally preferred.
  • the molding material from which the support core is formed in addition to the filler and the binder still contains water.
  • the water content of the molding material ie the mixture of filler, binder and water, is dependent on the binder content and is preferably 2 to 10 wt .-%, in particular 3 to 8 wt .-%. In view of a short drying time of the support core, the water content is as low as possible.
  • the polysaccharide binder preferably used according to the invention is also distinguished by a low hygroscopicity.
  • the residual moisture of the support core is not increased by moisture from the environment.
  • the residual moisture of the support core is preferably 0.1 to 0.8 wt .-%.
  • the strength of the support core decreases, while it becomes brittle at a residual moisture content of less than 0.1 wt .-%.
  • the invention ensures rapid drying of the support cores.
  • the flowability and processability of the molding material is significantly improved, so that the support cores can be produced with short cycle times, for example with a core shooter or with an isostatic press.
  • thermosetting plastic such as an epoxy resin
  • the curing of the plastic is carried out by the RTM method or by the vacuum injection method. That is, the wound with the reinforcing threads, ready-made support core is placed between the two tools, such as the upper and lower tool, a heated press, whereupon the reinforcing fibers are impregnated on the support core with the thermosetting plastic, in the cavity between the two Tool parts is injected in the support core is arranged.
  • thermosetting plastic under a pressure of 50 bar, in particular more than 80 bar or even 100 bar and more, are pressed into the cavity, while in the vacuum injection method of the thermosetting plastic in the cavity the prefabricated support core arranged therein is sucked. After curing of the resin is removed from the mold and the support core flushed with water, so that the fiber-reinforced structural hollow component is formed.
  • any structural hollow components made of fiber-reinforced plastic can be produced by the method according to the invention.
  • body parts can be produced, in particular the support columns, ie the A-, C-pillar collar, sills and bumpers.
  • the molding composition is: filler: 90.9% by weight Binder content (SE): 3.6% by weight Water content: 5.5% by weight
  • a molding material having the same sand as in Example 1 and an aqueous polyvinylpyrrolidone (PVP) solution is prepared.
  • the molding composition is: filler: 88.8% by weight Binder content (PVP): 3.2% by weight Water content: 8% by weight
  • the molding composition is: filler: 70.5% by weight Binder content (PVP): 8.5% by weight Water content: 21% by weight
  • a molding material is made from the same ceramic hollow spheres as in Comparative Example 2 and a carboxymethyl cellulose (CMS) / starch ether (SE) solution.
  • CMS carboxymethyl cellulose
  • SE starch ether
  • the binder composition is:
  • CMC solution / SE solution 40/60 CMC solution: about 15% by weight in water SE solution: about 35 wt .-% in water
  • the molding composition is: filler: 87.5% by weight Binder content (CMC / SE): 5% by weight Water content: 7.5% by weight
  • a molding material is made from the same sand as in Example 1 and an aqueous sodium polyphosphate solution.
  • the molding composition is: filler: 96% by weight Binder content: 2.5% by weight Water content: 1.5% by weight
  • a bending bar (22 ⁇ 22 ⁇ 170 mm) was produced in each case to determine the bending strength with a 3-point bending test machine.
  • the bender is broken between two supports by means of a movable punch in the middle and measured the force to be applied to the break.
  • the bending bars were produced under the same conditions on a core shooting machine.
  • the shooting pressure was set to 5 bar.
  • the subsequent drying time of the bending bars in the heated mold was at 150 ° C, each first 10 min. After removal from the mold, drying was continued for 30 minutes in a convection oven heated at 130 ° C. to ensure complete drying.
  • the bending test was carried out after the bends cooled for approx. 60 minutes at 22 ° C and an ambient air humidity between 40 and 55% relative humidity. The results are shown in the table below. ⁇ U> Table ⁇ / u> flexural strength (N / cm 2 ) example 1 630 Comparative Example 1 440 Comparative Example 2 500 Comparative Example 3 290 Comparative Example 4 280
  • Example 2 From the molding material according to Example 1, another test specimen was prepared in the same manner as the bending bar. The test specimen was subjected to a pressure of 200 bar in a high-pressure autoclave. The subsequent measurement of the length of the specimen with a sliding caliper showed no measurable change in length relative to the length of the specimen before treatment in the high-pressure autoclave.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Description

Die Erfindung bezieht sich auf ein Verfahren zur Herstellung eines Strukturhohlbauteils aus faserverstärktem Kunststoff nach dem Oberbegriff des Anspruchs 1.The invention relates to a method for producing a structural hollow component made of fiber-reinforced plastic according to the preamble of claim 1.

Zur Herstellung faserverstärkter Kunststoffhohlbauteile wird u.a. das sogenannte Resin Transfer Molding (RTM) - Verfahren und das Vakuum-Injektionsverfahren verwendet.For the production of fiber-reinforced plastic hollow components u.a. the so-called Resin Transfer Molding (RTM) method and the vacuum injection method used.

Dazu wird wenigstens eine Lage der z.B. uni- oder bidirektional gerichteten Verstärkungsfasern zwischen dem Ober- und dem Unterwerkzeug einer beheizten Presse gelegt und die Faserlage mit einem wärmehärtbaren Kunststoff, beispielsweise einem Epoxidharz mit Härter getränkt, der unter Druck in den Hohlraum mit der Faserlage zwischen Ober- und Unterwerkzeug injiziert wird. Ähnlich wird beim Vakuum-Injektionsverfahren vorgegangen, bei dem anstelle von Druck ein Vakuum angelegt wird, um den wärmehärtbaren Kunststoff in die Faserlage zu saugen.For this, at least one layer of e.g. uni- or bidirectionally directed reinforcing fibers placed between the upper and lower tool of a heated press and impregnated the fiber layer with a thermosetting plastic, such as an epoxy resin with hardener, which is injected under pressure into the cavity with the fiber layer between the upper and lower tool. Similarly, the vacuum-injection method is used, in which instead of pressure, a vacuum is applied to suck the thermosetting plastic in the fiber layer.

Für Automobile werden zahlreiche Strukturhohlbauteile verwendet, beispielsweise die Stützsäulen, Schweller, Stoßfänger und dergleichen. Diese Hohlbauteile werden dabei meist geklebt. Die Klebestelle kann jedoch zu einem Versagen führen.For automobiles numerous structural hollow components are used, for example the support columns, sills, bumpers and the like. These hollow components are usually glued. However, the splice can lead to failure.

Zudem lässt die Maßhaltigkeit geklebter Hohlbauteile zu wünschen übrig.In addition, the dimensional accuracy of bonded hollow components leaves much to be desired.

Für die Herstellung von Hohlbauteilen im RTM-Verfahren werden üblicherweise heute Schmelzkerne aus Wachs eingesetzt. Die dafür eingesetzten Prozesse sind wegen der Größe der Kerne sehr aufwändig. Weiterhin bedingt der große Wärmeausdehnungskoeffizient des Wachses eine aufwändige Abstimmung der notwenigen Fertigungsmittel. Nach der eigentlichen Bauteilherstellung werden die Materialien wieder ausgeschmolzen. Dabei verbleibt auf der Werkzeuginnenwand ein Restmaterial, was zum einen das Bauteilgewicht erhöht sowie kritisch hinsichtlich Emissionen und Lackverträglichkeit bewertet wird.For the production of hollow components in the RTM process usually melted cores made of wax are used today. The processes used for this are very complex because of the size of the cores. Furthermore, the large coefficient of thermal expansion of the wax requires a complex coordination of the necessary means of production. After the actual component production, the materials are melted out again. In the process, a residual material remains on the inner wall of the tool, which on the one hand increases the component weight and is critically evaluated with regard to emissions and paint compatibility.

Auch sind Stützkerne aus niedrigschmelzenden Wismutlegierungen verwendet worden. Wegen des hohen Energieaufwandes zum Schmelzen der Kerne, dem hohen Gewicht und der daraus resultierenden schwierigen Handhabbarkeit, aber auch wegen der Gesundheitsgefährdung durch Wismutdämpfe, sind diese Kerne in der Praxis jedoch nicht einsetzbar.Also, supporting cores have been used from low-melting bismuth alloys. Because of the high energy consumption for melting the cores, the high weight and the resulting difficult handling, but also because of the health risk of bismuth vapors, these cores are not used in practice.

Ferner werden Stützkerne aus hochdichtem Schaumstoff eingesetzt, die im Bauteil verbleiben und damit zu einer entsprechenden Gewichtserhöhung führen.Furthermore, support cores made of high-density foam are used, which remain in the component and thus lead to a corresponding increase in weight.

Aus WO 02/072328 A1 ist bereits ein Stützkern nach dem Oberbegriff des Anspruchs 1 bekannt. Als wasserlösliches organisches Bindemittel wird dabei Polyvinylpyrrolidon verwendet und als Füllstoff insbesondere Keramikhohlkugeln mit einem Durchmesser von etwa 120 µm. Die Suspension aus Wasser, Bindemittel und Füllstoff wird wie beim Schlickerguss in eine poröse Form gefüllt, um das Wasser abfließen zu lassen. Der Stützkern wird dann entformt und bei 120 °C mehrere Stunden getrocknet. Mit dem bekannten Verfahren können zwar Einzelstücke stücke gefertigt werden, zur Herstellung großer Stückzahlen ist es jedoch ungeeignet.Out WO 02/072328 A1 is already a support core according to the preamble of claim 1 is known. In this case, polyvinylpyrrolidone is used as the water-soluble organic binder and in particular ceramic hollow spheres with a diameter of about 120 μm as the filler. The suspension of water, binder and filler is filled in a porous mold as in slip casting to allow the water to drain. The support core is then demolded and dried at 120 ° C for several hours. Although with the known method unique pieces However, it is unsuitable for the production of large quantities.

Zum Umwickeln des Stützkerns kann eine Flechtanlage verwendet werden, wobei sich der Stützkern im Auge der Flechtanlage befindet, während die Verstärkungsfäden unter hoher Spannung von der Peripherie abgezogen werden. Wie sich gezeigt hat, hält der Stützkern nach WO 02/072328 A1 höheren Fadenabzugskräften aber nicht stand. Zudem hat sich gezeigt, dass sich mit dem bekannten Stützkern keine exakte Maßhaltigkeit erzielen lässt, insbesondere bei komplexen Strukturbauteilen. Auch wird durch die lange Trocknungszeit des Stützkerns die Herstellung des Strukturbauteils verzögert.For braiding the support core, a braiding system can be used, wherein the support core is in the eye of the braiding system, while the reinforcing threads are removed under high voltage from the periphery. As it has been shown, the support core keeps up WO 02/072328 A1 higher thread withdrawal forces but not stood. In addition, it has been shown that can be achieved with the known support core no exact dimensional stability, especially in complex structural components. Also, the production of the structural component is delayed by the long drying time of the support core.

Aus US-A-5262100 geht ein wasserdispergierbarer Stützkern aus einem wasserlöslichen, organischen Bindemittel und einem Füllstoff hervor. Der Füllstoff besteht zu mehr als 50 Gew.-% aus Sand. Das organische Bindemittel ist ein Kohlehydrat, beispielsweise Stärke. In US-A-5492660 wird ein Verfahren nach dem Oberbegriff des Anspruchs 1 beschrieben. Dabei werden als Füllstoff für den Stützkern Glashohlkugeln verwendet, und als Bindemittel anorganische Bindemittel, wie Natriumsilikat, sowie Bindemittel auf Aluminiumoxidbasis, sodass der Stützkern nur mit starken Säuren, wie Salzsäure, dispergiert werden kann.Out US-A-5262100 For example, a water-dispersible support core is made of a water-soluble organic binder and a filler. The filler consists of more than 50% by weight of sand. The organic binder is a carbohydrate, for example starch. In US-A-5492660 a method according to the preamble of claim 1 is described. In this case, hollow carbon spheres are used as the filler for the support core, and inorganic binders, such as sodium silicate, as well as binders based on alumina, so that the support core can be dispersed only with strong acids, such as hydrochloric acid.

Aufgabe der Erfindung ist es, ein Verfahren
bereitzustellen, mit dem auch komplexe faserverstärkte Strukturhohlbauteile hoher Festigkeit und Maßhaltigkeit in kurzer Zeit herstellbar sind.The object of the invention is a method
provide, with the complex fiber-reinforced structural hollow components of high strength and dimensional stability can be produced in a short time.

Dies wird erfindungsgemäß mit dem in Anspruch 1 gekennzeichneten Verfahren erreicht. In den übrigen Ansprüchen sind vorteilhafte Ausgestaltungen der Erfindung wiedergegeben.This is achieved according to the invention with the method characterized in claim 1. In the remaining claims advantageous embodiments of the invention are shown.

Erfindungsgemäß wird ein Stützkern hoher Festigkeit verwendet. So beträgt die 3-Punkt-Festigkeit des Stützkerns, deren Messung nachstehend näher erläutert ist, vorzugsweise mehr als 500 N/cm2, insbesondere mehr als 600 N/cm2.According to the invention, a support core of high strength is used. Thus, the 3-point strength of the support core, the measurement of which is explained in more detail below, is preferably more than 500 N / cm 2 , in particular more than 600 N / cm 2 .

Zum Umwickeln des Stützkerns kann daher eine Flechtanlage verwendet werden, in deren Auge sich der Stützkern befindet, während die'Verstärkungsfäden unter hoher Spannung von der Peripherie abgezogen werden. Dank seiner hohen Festigkeit hält der Stützkern diesen hohen Abzugskräften ohne weiteres stand.For wrapping the support core, therefore, a braiding system can be used, in whose eye the support core is, while the'Verstärkungsfäden be removed under high voltage from the periphery. Thanks to him high strength, the support core easily withstands these high pull-off forces.

Zugleich wird mit dem erfindungsgemäßen Stützkern eine hohe Maßhaltigkeit der damit hergestellten Strukturhohlbauteile, insbesondere nach dem RTM-Verfahren erreicht, und zwar auch bei komplexen Bauteilen. Dies ist auf die hohe Druckfestigkeit des erfindungsgemäßen Stützkerns zurückzuführen. So beträgt bei einfachen Bauteilen der Injektionsdruck, dem der mit der Faserlage umwickelte Stützkern ausgesetzt ist, normalerweise 50 bar oder weniger, während bei komplexen Bauteilen mit einem entsprechend höheren Faservolumengehalt ein Injektionsdruck von 80 bar und mehr erforderlich ist, damit der wärmehärtbare Kunststoff die Faserlage auf dem Stützkern einwandfrei durchtränkt. Schon die geringste Kompression des Stützkerns beim RTM-Verfahren führt jedoch zu einem Strukturhohlbauteil von nicht mehr genau definierter Wandstärke und damit zu Ausschuss. Der Stützkern zeichnet sich jedoch durch eine Druckfestigkeit von 80 bar, insbesondere 100 bar und mehr aus. Er ist daher in der Lage, hohen Injektionsdrücken beim RTM-Verfahren ohne weiteres standzuhalten.At the same time, with the support core according to the invention, a high dimensional stability of the structural hollow components produced therewith is achieved, in particular by the RTM method, and this also applies to complex components. This is due to the high compressive strength of the support core according to the invention. Thus, in simple components, the injection pressure to which the support core wrapped with the fiber layer is normally 50 bar or less, whereas for complex components having a correspondingly higher fiber volume content, an injection pressure of 80 bar and more is required, so that the thermosetting plastic on the fiber layer properly impregnated the support core. However, even the slightest compression of the support core in the RTM process leads to a structural hollow component of not exactly defined wall thickness and thus to rejects. However, the support core is characterized by a compressive strength of 80 bar, in particular 100 bar and more. He is therefore able to withstand high injection pressures in the RTM process easily.

Durch die Verwendung von Sand kann die hohe Festigkeit des Stützkerns bereits mit einer geringen Menge organischem Bindemittel erreicht werden. So beträgt der Anteil des Bindemittels vorzugsweise weniger als 10 Gew.-%, insbesondere weniger als 5 Gew.-%, bezogen auf das Gewicht des Füllstoffs. Dies hat eine entsprechende Herabsetzung des Wassergehalts und damit eine kurze Trocknungszeit mit einer entsprechend kurzen Herstellungszeit des Stützkerns und somit kurze Zykluszeiten zur Folge. In Fällen, bei denen es auf die Trocknungszeit nicht entscheidend ankommt, beispielsweise bei der Prototypen-Fertigung, können jedoch auch höhere Bindemittelgehalte zur Anwendung kommen.By using sand, the high strength of the support core can already be achieved with a small amount of organic binder. Thus, the proportion of the binder is preferably less than 10 wt .-%, in particular less than 5 wt .-%, based on the weight of the filler. This has a corresponding reduction of the water content and thus a short drying time with a correspondingly short production time of the support core and thus short cycle times result. In cases where drying time is not critical, For example, in the prototype production, but also higher binder contents can be used.

Vorzugsweise beträgt der Anteil des Bindemittels des Stützkerns jedoch mindestens 2 Gew.-%, bezogen auf das Gewicht des Füllstoffs, um eine hinreichende Festigkeit zu erreichen.However, the proportion of the binder of the support core is preferably at least 2 wt .-%, based on the weight of the filler in order to achieve a sufficient strength.

Als Sand wird vorzugsweise Quarzsand verwendet, jedoch sind auch andere Sände zur Herstellung des Stützkerns einsetzbar, beispielsweise Zirkonsand oder Cerabead.As sand preferably quartz sand is used, but other Sände are used for the production of the support core, such as zircon sand or Cerabead.

Die mittlere Korngröße des Sandes liegt vorzugsweise zwischen 100 µm und 800 µm, insbesondere zwischen 200 µm und 500 µm.The mean grain size of the sand is preferably between 100 .mu.m and 800 .mu.m, in particular between 200 .mu.m and 500 .mu.m.

Der Stützkern kann mit einer Kernschießmaschine, wie sie beispielsweise in DE 102 00 927 A1 beschrieben ist, in die Form mit Druckluft eingeschossen werden, weil der Sand die erforderliche Fließfähigkeit oder Fluidisierbarkeit des Formstoffs sicherstellt. Auch kann der Stützkern durch Pressen hergestellt werden, z.B. mit einem Formwerkzeug, bei dem der Formstoff mit einem Kolben in die Form gepresst wird.The support core can be used with a core shooter, as for example in DE 102 00 927 A1 is injected into the mold with compressed air, because the sand ensures the required flowability or fluidizability of the molding material. Also, the support core can be made by pressing, for example with a mold, wherein the molding material is pressed with a piston in the mold.

Der Füllstoff kann vollständig aus Sand bestehen, jedoch ist als Füllstoff auch ein Gemisch einsetzbar, das aus Sand und Blähglasgranulat besteht. Blähglasgranulat ist ein Glas-Recyclingprodukt, das insbesondere zur Schall- und Wärmeisolierung eingesetzt wird. Zur Herstellung von Blähglasgranulat wird Altglas gemahlen, das dabei gebildete Glasmehl mit Wasser, Binde- und Blähmittel vermischt und daraus unter Aufschäumen des Blähmittels in einem Drehrohrofen bei etwa 900 °C das kugelförmige Granulat gebildet. Die mittlere Korngröße des Blähglasgranulats beträgt vorzugsweise 100 µm bis 800 µm, insbesondere 200 µm bis 500 µm. Durch die Verwendung von Blähglasgranulat kann die Trocknungszeit weiter reduziert werden.The filler can be made entirely of sand, but as a filler and a mixture can be used, which consists of sand and expanded glass granules. Expanded glass granulate is a glass recycling product that is used in particular for sound and heat insulation. To produce expanded glass granules, scrap glass is ground, the glass powder formed in the process is mixed with water, binding agent and blowing agent, and the spherical granules are formed from this by foaming the blowing agent in a rotary kiln at about 900 ° C. The mean grain size of the expanded glass granules is preferably 100 .mu.m to 800 .mu.m, in particular 200 .mu.m to 500 .mu.m. By using expanded glass granules, the drying time can be further reduced.

Der Sand kann jedoch auch mit weiteren Füllstoffen vermischt werden, beispielsweise mit Hohlkugeln, wie Keramikhohlkugeln, z.B. mit einem mittleren Durchmesser von 50 m bis 400 µm. Auch sind Gemische aus Sand, Blähglasgranulat und Hohlkugeln als Füllstoff für den Stützkern einsetzbar.However, the sand can also be mixed with other fillers, for example with hollow spheres, such as hollow ceramic spheres, e.g. with a mean diameter of 50 m to 400 μm. Also, mixtures of sand, expanded glass granules and hollow spheres can be used as filler for the support core.

Der Anteil des Sandes des Stützkerns beträgt jedoch mehr als 50 Gew.-% des Füllstoffs, vorzugsweise mehr als 70 Gew.-%, insbesondere 90 Gew.-% und mehr.However, the proportion of the sand of the support core is more than 50 wt .-% of the filler, preferably more than 70 wt .-%, in particular 90 wt .-% and more.

Als organisches Bindemittel wird ein Polysaccharid-Bindemittel verwendet. Das Polysaccharid-Bindemittel kann ein Bindemittel auf Cellulosebasis sein, insbesondere Carboxymethylcellulose. Vorzugsweise wird als Polysaccharid-Bindemittel jedoch ein Bindemittel auf Stärkebasis verwendet, insbesondere Stärkeether, da ein Bindemittel auf Stärkebasis bei gleichem Gewichtsanteil zu einer besonders hohen Festigkeit führt. Jedoch sind auch Gemische aus einem Bindemittel auf Cellulosebasis und einem Bindemittel auf Stärkebasis, also z.B. aus Carboxymethylcellulose und Stärkeether, einsetzbar.As the organic binder, a polysaccharide binder is used. The polysaccharide binder may be a cellulose based binder, especially carboxymethylcellulose. Preferably, however, a starch-based binder is used as polysaccharide binder, in particular starch ether, since a starch-based binder at the same weight fraction leads to a particularly high strength. However, blends of a cellulose-based binder and a starch-based binder, e.g. from carboxymethyl cellulose and starch ether, can be used.

Der Anteil des Bindemittels auf Stärkebasis beträgt vorzugsweise mehr als 70 Gew.-% des Bindemittels. Ein Bindemittel, das ganz, also zu mehr als 97 Gew.-% aus einem Bindemittel aus Stärkebasis, also insbesondere Stärkeether, besteht, wird jedoch im Allgemeinen bevorzugt.The proportion of the starch-based binder is preferably more than 70% by weight of the binder. However, a binder which consists entirely, that is more than 97% by weight, of a starch-based binder, ie in particular starch ether, is generally preferred.

Der Formstoff, aus dem der Stützkern gebildet wird, enthält neben dem Füllstoff und dem Bindemittel noch Wasser. Der Wasseranteil des Formstoffs, also des Gemischs aus Füllstoff, Bindemittel und Wasser, ist vom Bindemittelgehalt abhängig und beträgt vorzugsweise 2 bis 10 Gew.-%, insbesondere 3 bis 8 Gew.-%. Im Hinblick auf eine kurze Trocknungszeit des Stützkerns ist der Wassergehalt möglichst gering.The molding material from which the support core is formed, in addition to the filler and the binder still contains water. The water content of the molding material, ie the mixture of filler, binder and water, is dependent on the binder content and is preferably 2 to 10 wt .-%, in particular 3 to 8 wt .-%. In view of a short drying time of the support core, the water content is as low as possible.

Das erfindungsgemäß bevorzugt verwendete Polysaccharid-Bindemittel zeichnet sich zudem durch eine geringe Hygroskopizität aus. Damit wird die Restfeuchte des Stützkerns durch Feuchtigkeit aus der Umgebung nicht erhöht. Die Restfeuchte des Stützkerns beträgt vorzugsweise 0,1 bis 0,8 Gew.-%. Bei einer Restfeuchte von über 0,8 Gew.-% nimmt die Festigkeit des Stützkerns ab, während er bei einer Restfeuchte von weniger als 0,1 Gew.-% spröde wird.The polysaccharide binder preferably used according to the invention is also distinguished by a low hygroscopicity. Thus, the residual moisture of the support core is not increased by moisture from the environment. The residual moisture of the support core is preferably 0.1 to 0.8 wt .-%. At a residual moisture of over 0.8 wt .-%, the strength of the support core decreases, while it becomes brittle at a residual moisture content of less than 0.1 wt .-%.

Durch die Erfindung wird eine schnelle Trocknung der Stützkerne sichergestellt. Zudem wird die Fließfähigkeit und Verarbeitbarkeit des Formstoffs deutlich verbessert, so dass die Stützkerne mit kurzen Taktzeiten beispielsweise mit einer Kernschießmaschine oder mit einer isostatischen Presse hergestellt werden können.The invention ensures rapid drying of the support cores. In addition, the flowability and processability of the molding material is significantly improved, so that the support cores can be produced with short cycle times, for example with a core shooter or with an isostatic press.

Das Tränken der Fasern auf dem Stützkern mit einem wärmehärtbaren Kunststoff, beispielsweise einem Expoxidharz, und das Aushärten des Kunststoffs erfolgt nach dem RTM-Verfahren oder nach dem Vakuum-Injektions-Verfahren . D.h., der mit den Verstärkungsfäden umwickelte, konfektionierte Stützkern wird zwischen die beiden Werkzeuge, also beispielsweise das Ober- und das Unterwerkzeug, einer beheizten Presse gelegt, worauf die Verstärkungsfasern auf dem Stützkern mit dem wärmehärtbaren Kunststoff imprägniert werden, der in den Hohlraum zwischen den beiden Werkzeugteilen injiziert wird, in dem der Stützkern angeordnet ist. Dabei kann erfindungsgemäß bei dem RTM-Verfahren der wärmehärtbare Kunststoff unter einem Druck von 50 bar, insbesondere mehr als 80 bar oder gar 100 bar und mehr, in den Hohlraum gepresst werden, während beim Vakuum-Injektions-Verfahren der wärmehärtbare Kunststoff in den Hohlraum mit dem darin angeordneten konfektionierten Stützkern gesaugt wird. Nach dem Aushärten des Harzes wird entformt und der Stützkern mit Wasser ausgeschwemmt, so dass das faserverstärkte Strukturhohlbauteil gebildet wird.The impregnation of the fibers on the support core with a thermosetting plastic, such as an epoxy resin, and the curing of the plastic is carried out by the RTM method or by the vacuum injection method. That is, the wound with the reinforcing threads, ready-made support core is placed between the two tools, such as the upper and lower tool, a heated press, whereupon the reinforcing fibers are impregnated on the support core with the thermosetting plastic, in the cavity between the two Tool parts is injected in the support core is arranged. In this case, according to the invention in the RTM process, the thermosetting plastic under a pressure of 50 bar, in particular more than 80 bar or even 100 bar and more, are pressed into the cavity, while in the vacuum injection method of the thermosetting plastic in the cavity the prefabricated support core arranged therein is sucked. After curing of the resin is removed from the mold and the support core flushed with water, so that the fiber-reinforced structural hollow component is formed.

Nach dem erfindungsgemäßen Verfahren können beliebige Strukturhohlbauteile aus faserverstärktem Kunststoff hergestellt werden. Im Automobilbereich sind vor allem Karosseriebauteile herstellbar, insbesondere die Stützsäulen, also die A-, Bund C-Säule, Schweller und Stoßfänger.Any structural hollow components made of fiber-reinforced plastic can be produced by the method according to the invention. In the automotive sector, especially body parts can be produced, in particular the support columns, ie the A-, C-pillar collar, sills and bumpers.

Beispiel 1example 1

Es wird ein Formstoff aus Quarzsand (mittlere Korngröße 320 µm) und einer wässerigen Stärkeether(SE)-Lösung hergestellt.It is a molding material made of quartz sand (average grain size 320 microns) and an aqueous starch ether (SE) solution.

Die Formstoffzusammensetzung beträgt: Füllstoffgehalt: 90,9 Gew.-% Bindemittelgehalt (SE): 3,6 Gew.-% Wassergehalt: 5,5 Gew.-% The molding composition is: filler: 90.9% by weight Binder content (SE): 3.6% by weight Water content: 5.5% by weight

Vergleichsbeispiel 1Comparative Example 1

Es wird ein Formstoff mit dem gleichen Sand wie in Beispiel 1 und einer wässerigen Polyvinylpyrrolidon(PVP)-Lösung hergestellt.A molding material having the same sand as in Example 1 and an aqueous polyvinylpyrrolidone (PVP) solution is prepared.

Die Formstoffzusammensetzung beträgt: Füllstoffgehalt: 88,8 Gew.-% Bindemittelgehalt (PVP): 3,2 Gew.-% Wassergehalt: 8 Gew.-% The molding composition is: filler: 88.8% by weight Binder content (PVP): 3.2% by weight Water content: 8% by weight

Vergleichsbeispiel 2Comparative Example 2

Es wird ein Formstoff aus Keramikhohlkugeln (mittlerer Durchmesser 0,14 mm) und einer wässerigen PVP-Lösung hergestellt.It is a molding material made of hollow ceramic balls (average diameter 0.14 mm) and an aqueous PVP solution.

Die Formstoffzusammensetzung beträgt: Füllstoffgehalt: 70,5 Gew.-% Bindemittelgehalt (PVP): 8,5 Gew.-% Wassergehalt: 21 Gew.-% The molding composition is: filler: 70.5% by weight Binder content (PVP): 8.5% by weight Water content: 21% by weight

Vergleichsbeispiel 3Comparative Example 3

Es wird ein Formstoff aus den gleichen Keramikhohlkugeln wie im Vergleichsbeispiel 2 und einer Carboxymethylcellulose(CMS)/Stärkeether(SE)-Lösung hergestellt.A molding material is made from the same ceramic hollow spheres as in Comparative Example 2 and a carboxymethyl cellulose (CMS) / starch ether (SE) solution.

Die Bindemittelzusammensetzung beträgt:The binder composition is:

Volumenverhältnis CMC-Lösung/SE-Lösung = 40/60 CMC-Lösung: ca. 15 Gew.-% in Wasser SE-Lösung: ca. 35 Gew.-% in Wasser Volume ratio CMC solution / SE solution = 40/60 CMC solution: about 15% by weight in water SE solution: about 35 wt .-% in water

Die Formstoffzusammensetzung beträgt: Füllstoffgehalt: 87,5 Gew.-% Bindemittelgehalt (CMC/SE): 5 Gew.-% Wassergehalt: 7,5 Gew.-% The molding composition is: filler: 87.5% by weight Binder content (CMC / SE): 5% by weight Water content: 7.5% by weight

Vergleichsbeispiel 4Comparative Example 4

Es wird ein Formstoff aus dem gleichen Sand wie in Beispiel 1 und einer wässerigen Natriumpolyphosphat-Lösung hergestellt.A molding material is made from the same sand as in Example 1 and an aqueous sodium polyphosphate solution.

Die Formstoffzusammensetzung beträgt: Füllstoffgehalt: 96 Gew.-% Bindemittelgehalt: 2,5 Gew.-% Wassergehalt: 1,5 Gew.-% The molding composition is: filler: 96% by weight Binder content: 2.5% by weight Water content: 1.5% by weight

Aus dem Formstoff nach dem Beispiel 1 und den Vergleichsbeispielen 1 bis 4 wurde jeweils ein Biegeriegel (22 x 22 x 170 mm) hergestellt, um mit einer 3-Punkt-Biegeprüfmaschine die Biegefestigkeit zu bestimmen. Dabei wird der Biegeriegel zwischen zwei Auflagern mittels eines beweglichen Stempels in der Mitte gebrochen und die für den Bruch aufzuwendende Kraft gemessen.From the molding material according to Example 1 and Comparative Examples 1 to 4, a bending bar (22 × 22 × 170 mm) was produced in each case to determine the bending strength with a 3-point bending test machine. Here, the bender is broken between two supports by means of a movable punch in the middle and measured the force to be applied to the break.

Die Biegeriegel wurden unter gleichen Bedingungen auf einer Kernschießmaschine hergestellt. Der Schießdruck wurde auf 5 bar festgelegt. Die anschließende Trocknungszeit der Biegeriegel im beheizten Werkzeug betrug bei 150 °C jeweils zunächst 10 min. Nach dem Entformen wurde zur Sicherstellung einer vollständigen Trocknung für 30 min in einem bei 130 °C beheizten Konvektionsofen nachgetrocknet. Die Biegeprüfung wurde durchgeführt, nachdem die Biegeriegel ca. 60 min bei 22 °C und einer Umgebungsluftfeuchte zwischen 40 und 55 % relative Feuchte auskühlten. Die Ergebnisse sind in der nachstehenden Tabelle wiedergegeben. Tabelle Biegefestigkeit
(N/cm2) Beispiel 1 630 Vergleichsbeispiel 1 440 Vergleichsbeispiel 2 500 Vergleichsbeispiel 3 290 Vergleichsbeispiel 4 280 The bending bars were produced under the same conditions on a core shooting machine. The shooting pressure was set to 5 bar. The subsequent drying time of the bending bars in the heated mold was at 150 ° C, each first 10 min. After removal from the mold, drying was continued for 30 minutes in a convection oven heated at 130 ° C. to ensure complete drying. The bending test was carried out after the bends cooled for approx. 60 minutes at 22 ° C and an ambient air humidity between 40 and 55% relative humidity. The results are shown in the table below. <U> Table </ u> flexural strength
(N / cm 2 ) example 1 630 Comparative Example 1 440 Comparative Example 2 500 Comparative Example 3 290 Comparative Example 4 280

Aus dem Formstoff nach dem Beispiel 1 wurde ein weiterer Prüfkörper in gleicher Weise wie der Biegeriegel hergestellt. Der Prüfkörper wurde in einem Hochdruck-Autoklaven einem Druck von 200 bar unterworfen. Die anschließende Messung der Länge des Prüfkörpers mit einer Schiebelehre ergab keine messbare Längenänderung gegenüber der Länge des Prüfkörpers vor der Behandlung in dem Hochdruck-Autoklaven.From the molding material according to Example 1, another test specimen was prepared in the same manner as the bending bar. The test specimen was subjected to a pressure of 200 bar in a high-pressure autoclave. The subsequent measurement of the length of the specimen with a sliding caliper showed no measurable change in length relative to the length of the specimen before treatment in the high-pressure autoclave.

Claims (10)

  1. A method for producing a hollow structural component from fibre-reinforced plastics material with a water-dispersible support core, the support core being formed from a moulding material made of a watersoluble binding agent, a filler and water using a moulding tool, dried and then provided with reinforcement fibres, whereupon the fibres on the support core, by means of the resin transfer moulding method (RTM) or the vacuum injection method, are saturated with a curable plastics material, the plastics material is cured and the support core is flushed with water, characterised in that, for the moulding material, from which the support core is formed, more than 50 % by weight of sand is used as the filler and a polysaccharide binding agent is used as the binding agent.
  2. A method according to claim 1, characterised in that the RTM method is carried out at an injection pressure of more than 80 bar.
  3. A method according to claim 1 or claim 2, characterised in that the sand has a mean grain size of 100 to 800 µm.
  4. A method according to any one of claims 1 to 3, characterised in that the filler additionally contains blown glass granulate and/or hollow balls.
  5. A method according to any one of the preceding claims, characterised in that the proportion of the binding agent in the support core is 2 to 10 % by weight based on the weight of the filler.
  6. A method according to claim 5, characterised in that the proportion of the binder in the support core is at most 5 % by weight based on the weight of the filler.
  7. A method according to claim 1, characterised in that the polysaccharide binding agent is a binding agent based on starch.
  8. A method according to claim 7, characterised in that the proportion of the binding agent based on starch is at least 70 % by weight of the polysaccharide binding agent.
  9. A method according to claim 7 or claim 8, characterised in that the binding agent based on starch is starch ether.
  10. A method according to any one of the preceding claims, characterised in that the support core, after drying, has a residual moisture of 0.1 to 0.8 % by weight.
EP20060009821 2005-06-29 2006-05-12 Method for producing fibre reinforced hollow objects with a water dispersible core Expired - Fee Related EP1745908B1 (en)

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DE200510030256 DE102005030256A1 (en) 2005-06-29 2005-06-29 Water-dispersible core support for production of an automobile hollow structural component from fiber-reinforced plastic, made of a water-soluble starch ether binding agent and a filler composed of sand

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DE102008019065B4 (en) * 2008-04-15 2011-06-16 Airbus Operations Gmbh Process for producing a core composite provided with cover layers on both sides and core composite
EP2145751A1 (en) 2008-07-18 2010-01-20 Euro-Composites S.A. Method for producing a hollow body from fibre compound plastic
EP2335899A1 (en) 2009-12-17 2011-06-22 EUROCOPTER DEUTSCHLAND GmbH A method of fabricating an improved mold core and a mold core obtained by said method
DE102011113200B4 (en) * 2011-09-10 2017-10-12 Volkswagen Aktiengesellschaft A method for producing a hollow profile node of a fiber-plastic composite for the connection of hollow profile components of a frame member
DE102013106876A1 (en) 2013-07-01 2015-01-08 C.F. Maier GmbH & Co. KG Mold core and method for producing fiber-reinforced structural hollow components
EP2871044A1 (en) 2013-11-12 2015-05-13 AIRBUS HELICOPTERS DEUTSCHLAND GmbH Method for producing a fibre-reinforced plastic component and mould core for use in such method
CN106670390B (en) * 2016-11-21 2018-11-02 湖北三江航天红阳机电有限公司 A kind of solvable sand core forming method of band Dome winding shell

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WO2011085450A1 (en) * 2010-01-15 2011-07-21 Ip Plastics Pty Ltd Method of forming plastics products of complex shape
DE102013022247A1 (en) 2013-12-09 2015-06-11 Audi Ag Vehicle body element
DE102013022247B4 (en) 2013-12-09 2019-01-24 Audi Ag Vehicle body element

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